D.R. Lanctot

The objective of this review is to provide basic information pertaining to biomechanical aspects of bone as they relate to tissue engineering. The review is written for the general tissue engineering reader, who may not have a biomechanical engineering background. To this end, biomechanical characteristics and properties of normal and repair cortical and cancellous bone are presented. Also, this chapter intends to describe basic structure-function relationships of these two types of bone. Special emphasis is placed on salient classical and modern testing methods, with both material and structural properties described.

Secure arthroscopic repair of rotator cuff tears and Bankart lesions requires tight knots (knot security). Equally important, but usually overlooked, is the tightness of the suture loop (loop security). This study compared loop security in knots tied with No. 1 PDS suture using three different methods: (1) hand-tied, (2) single-hole standard knot pusher, and (3) cannulated double-diameter knot pusher. The results of this study show that the double-diameter knot pusher maintained tight suture loops that were equivalent in circumference to hand-tied loops and were significantly tighter than suture loops tied with a standard single-hole knot pusher. This study highlights the fact that loop security is equally important to knot security in tissue fixation.

The objective of this study was to provide a map of cartilage biomechanical properties, thickness, and histomorphometric characteristics in the human, cadaveric first metatarsophangeal joint, to determine if normal articular cartilage was predisposed topographically to biomechanical mismatches in articulating surfaces. Cartilage intrinsic material properties and thickness were obtained from seven pairs of human, freshly frozen, cadaveric, metatarsophalangeal joints using an automated creep indentation apparatus under conditions of biphasic creep. Eight sites were tested: four on the metatarsal head, two on the proximal phalanx base, and one on each sesamoid bone to obtain the aggregate modulus, Poisson's ratio, permeability, shear modulus, and thickness. Cartilage in the lateral phalanx site of the left metatarsal head had the largest aggregate modulus (1.34 MPa), whereas the softest tissue was found in the right medial sesamoid (0.63 MPa). The medial phalanx region of the right joint was the most permeable (4.56 x 10(-15) meter4/Newton-second), whereas the medial sesamoid articulation of the metatarsal head of the left joint was the least permeable (1.26 x 10(-15) meter4/Newton-second). Material properties and thickness are indicative of the tissue's functional environment. The lack of mismatches in cartilage biomechanical properties of the articulating surfaces found in this study may be supportive of clinical observations that early degenerative changes, in the absence of traumatic events, do not occur at the selected test sites in the human first metatarsophalangeal joint.

Viscoelastic inserts are commonly used as artificial shock absorbers to prevent neuropathic foot ulcerations by decreasing pressure on the sole of the foot. Unfortunately, there is little scientific information available to guide physicians in the selection of appropriate insole materials. Therefore, a novel methodology was developed to form a rational platform for biomechanical characterizations of insole material durability, which consisted of in vivo gait analysis and in vitro bioengineering measurements. Results show significant differences in the compressive stiffness of the tested insoles and the rate of change over time in both compressive stiffness and peak pressures measured. Good correlations were found between pressure-time integral and Young's modulus (r2 = 0.93), and total energy applied and Young's modulus (r2 = 0.87).